My nephew bought his first handgun an anib used M&P Compact from a "friend" without realizing the cost of .357 Sig ammo. My thought is to recommend he get a second barrel in .40 to keep his shooting costs down.

Some questions........(I'm a 3rd generation guy, and don't own any striker fired guns )

Can you change a S&W M&P compact from .357 Sig to .40 S&W?
Do you need to change the recoil spring?
Would the new barrel need to be fitted or would it be a simple drop-in?

Thanks
BAM